1. Field of the Invention
The present invention relates to a coupling adjusting structure for a double-tuned circuit which is suitably used for a TV tuner and the like.
2. Description of the Related Art
A configuration of a known coupling adjusting structure for a double-tuned circuit will be described with reference to FIG. 11. A printed circuit board 51 has a variety of electrical components (not shown) disposed thereon including first and second tuned circuits 52 and 53 formed side by side.
First and second coils 54 and 55 serving as a part of the first and second tuned circuits 52 and 53 have windings 54a and 55a formed by winding wires, and two pairs of fixing legs 54b and 55b disposed at the ends of the windings 54a and 55a, respectively.
The first and second coils 54 and 55 are configured such that the windings 54a and 55a are mounted on the printed circuit board 51 in an upright manner while being close to each other, and the fixing legs 54b and 55b are passed through the printed circuit board 51 and soldered to corresponding conductive patterns (not shown) formed on the lower surface of the printed circuit board 51.
In the double-tuned circuit having such a configuration, an inductive coupling is adjusted by deforming free corresponding ends of the mutually opposing windings 54a and 55a of the first and second coils 54 and 55 in the opposing directions indicated by the arrows Z in the figure.
The known coupling adjusting structure for a double-tuned circuit is configured such that the windings 54a and 55a are disposed in an upright manner against the printed circuit board 51 so as to deform a part of each of the windings 54a and 55a of the first and second coils 54 and 55, respectively, giving rise to a problem in that the double-tuned circuit is tall.
Accordingly, it is an object of the present invention to provide a thin and easily-adjustable coupling adjusting structure for a double-tuned circuit.
In view of the above described problem, according to one aspect of the present invention, a coupling adjusting structure for a double-tuned circuit, comprises: a printed circuit board; a first tuned circuit comprising a first coil formed by a combination of first and second conductive patterns formed on first and second surfaces of the printed circuit board, respectively; and a second tuned circuit comprising a second coil formed by another combination of other first and second conductive patterns formed on the first and second surfaces of the printed circuit board, respectively. The first and second coils are configured such that the first conductive patterns formed on the first surface of the printed circuit board and the corresponding second conductive patterns formed on the second surface of the printed circuit board are connected to each other via corresponding connecting conductors, one end of the first coil and the corresponding end of the second coil are disposed close to each other, at least one first ground conductive pattern is disposed at least on the first surface of the printed circuit board, and at least one first jumper connected to the first ground conductive pattern is disposed between the first and second coils so as to adjust an inductive coupling of the double-tuned circuit.
In the coupling adjusting structure for a double-tuned circuit, a first island conductive pattern which is out of conduction with the first ground conductive pattern is preferably provided between the first and second coils and on the first surface of the printed circuit, and the first jumper is preferably connected to the first ground conductive pattern and the first island conductive pattern.
Also, in the coupling adjusting structure for a double-tuned circuit, at least one second ground conductive pattern and a second island conductive pattern which lies between the first and second coils and which is out of conduction with the second ground conductive pattern are preferably provided on the second surface of the printed circuit board, the first and second ground conductive patterns are preferably connected to each other via a conductor, and the first and second island conductive patterns are preferably connected to each other via another conductor.
In addition, in the coupling adjusting structure for a double-tuned circuit, at least one second jumper is preferably connected to the second ground conductive pattern and the second island conductive pattern so as to adjust the inductive coupling.
According to another aspect of the present invention, a coupling adjusting structure for a double-tuned circuit comprises: a printed circuit board; a first tuned circuit comprising a first coil formed by a combination of first and second conductive patterns formed on first and second surfaces of the printed circuit board, respectively; and a second tuned circuit comprising a second coil formed by another combination of other first and second conductive patterns formed on the first and second surfaces of the printed circuit board, respectively. The first and second coils are configured such that the first conductive patterns formed on the first surface of the printed circuit board and the corresponding second conductive patterns formed on the second surface of the printed circuit board are connected to each other via corresponding connecting conductors, one end of the first coil and the corresponding end of the second coil are disposed close to each other, at least one first ground conductive pattern comprising a first adjusting conductive pattern extending between the first and second coils is disposed at least on the first surface of the printed circuit board, and the first adjusting conductive pattern is cut off by at least one first break so as to adjust an inductive coupling of the double-tuned circuit.
In the coupling adjusting structure for a double-tuned circuit, at least one second ground conductive pattern comprising a second adjusting conductive pattern extending between the first and second coils is preferably provided on the second surface of the printed circuit board, and the first and second ground conductive patterns are preferably connected to each other via a conductor.
Also, in the coupling adjusting structure for a double-tuned circuit, the second adjusting conductive pattern is preferably cut off by at least one second break so as to adjust the inductive coupling.